Straightforward trunking system



Aug. 9 1927.

. 1,638,430 R. s. BAILEY ET AL STRAIGHTFORWARD TRUNKING SYSTE M Filed Sept.18. 1924 4 Sheets-Sheet l R. S. BAILEY ET AL STRAIGHTFORWARD TRUNKING SYSTEM Filed Sept. 18. 1924 4 Sheets-Sheet 2 Aug. 9, 1927.

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Panda? [Sn/7e fdyarfi'firae V 1 538 430 1927' I R. s. BAILEY ET AL smuenwoawmn wnuuxme SYSTEM Filed Sept. 18, 1924 4 Sheets-Sheet 4 Patented Aug. 9, 1927.

UNITED STATES insane PATENT OFFICE.

RAND S. BAILEY, OF MONTCLAIR, NEW JERSEY, AND EDGAR P. BROE, OF NEW YORK,

N. Y., ASSIGNORS TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A GOR- PORA'IION OF NEW YORK.

STRAIGHTFORWARD TRUNKING SYSTEM.

Application filedseptember 18, 1924. Serial No. 738,488.

This invention relates to telephone ex change systems and more particularly to trunking systems wherein A and B operators are employed in trunking calls bev tween exchanges. In such systems, it' is customary for the A operators to receive the calls from the calling subscribers and to extend them over a trunk line to a B opera-" for in the proper exchange whlch B operator then proceeds to complete the connection. v

An object of the invention is to indicate to the Aoperators the busy or idle condition of the B operators to whom she has trunk circuits.

A further object of the invention 'is to automatically connect a B operators telephone to concurrently calling trunks in a predetermined sequential order.

The principal feature of the invention resides in arranging the trunks between an A operators position and. each B position in separate groups at the A position; locating before the A operator a signal corresponding toeach group of trunks and providing circuit arrangements whereby when a B operator is at her position and idle, a corresponding signal will be displayed before each A operator having trunks to that B operator and whereby said signals will be retired when the B operator becomes busy or leaves the position.

Another feature of the invention resides in such an arrangement of circuits that when all of the B operators at the same exchange are simultaneouslybusy, the corresponding signals at the A positions will be displayed.-

lVhen an A operator selects an idle 40 trunk in a group terminating in an occupied B position at which the B operator is idle as shown by the display of the corresponding group busy signal in the A position, the B operators telephone is automatically connected to the calling trunk. After receiving the details of the desired connection from the A operator over the trunk, the B operatorproceeds to complete the connection by placing the plug of'the calling trunk into the outgoing jack of the desired line circuit after which her telephone is automatically disconnected and tial order.

is readyto be connected to another trunk in a similar manner. In case, however, a plurality of concurrent calls are received at the B operators position while she is engaged with a previous call, her telephone set when disconnected will be automatically connected .to the trunks on which calls are waiting in a definite predetermined sequen- Another feature of the invention therefore resides in providing a chain circuit arrangement at the B position whereby when a plurality of concurrent calls are received over the trunks terminating at the position the operators telephone thereat will'be automatically connected to the calling trunks in a predetermined definite sequential order.

Other features of the invention will be'7 apparent from the following detailed de scription and the drawings wherein- Figure 1 shows the trunk jacks and position busysig'nals located at a single A operators position. I

F ig; 2 shows two groups of trunks each terminating at a different B operators position, the incoming ends of each trunk terminating in acpl'u i Fig. 3 shows the circuit for automatically a0 connecting the B operators telephonesets'- with the trunks. I

Fig. 4 shows two B operators positions with the telephone sets and control relays.

Referring to Fig. 1', it will be noted that the trunk jacks as illustrated are shown in two groups each group being provided with a common indicating lamp:

Referring to Fig. 2, it will be noted that two groups of talking trunks are illustrated,

but that the details of only a single trunk are shown in each group. p l

Referring to Fig. 3, the upper portion of the drawing shows in detail the control circuits for three trunks for'transfer'ring the operators telephone set to a selected trunk while the lower portion of the drawing shows the circuits in detail for'No. 1 and No. 3 trunk." I I Referring to Fig. 4, two operators tele phone sets are shown. Each operators set comprises the usual transmitter and receiver terminating in twin plugs arranged. to be; inserted in twin jacks connecting with the usual repeating coil circuit. In addition to the repeating coil, a series of control relays are shown.

Various details of the circuits will be pointed out in describing the operation of the system, which is as follows:

Referring first to Fig. 4.- when the plugs V and \V of the operators telephone '2" are placed in the jacks T and U the tollowing operation takes place:

Relay A associated with the operators position is operated as follows: ground, bat: tery, winding of relay A l, spring 2 of jack T tip conductor 3 of the plug V at, transmitter 5, 6, '4', S, 9, 10, to ground. Helay A operating, completes the circuit of relay B and this latter relay in operating completes the circuit of relay E Fig. 'l, as follows: ground, contacts of relay B 'li', contacts of relay D 18, Figs. 3, 2 and 1, and winding of relay E to battery a d ground.

The operation of relay E completes the circuit of lamp X indicating to the A? operator that the B operator is at her position and idle.

Relay A is operated when the plugs V and Vi are inserted in the jacks T 2 and U and causes the operation of relay B. The operation of relay B completes the clrcnit of relay E as follows: ground, contacts of relay B contacts of relay D 22, Flgs. 3, 2 and 1 and winding of relay E to bat-- tery and ground. The operation of relay E completes the circuit of lamp X notifying the A operator that this B operators position is also occupied and that the operator is idle.

In case the B operator at the first pos1- tion withdraws the plug V from the jack, then relay A restores thereby releasing relay B thus completing the circuit of relay D to ground through contacts of relay B The release of relay B and the operation of relay D opens the circuit of relay E thereby extinguishing lamp X and connects the conductor extending from the right-h and armature of relay D to the winding of relay X. In case the second B operator should withdraw the plug from the jacs then relay A would restore thereby releasing relay B which in restoring would complete the circuit of relay D Upon the release of relay B and the operation of relay I) the circuit of relay E is opened thereby extinguishing lamp X and the circuit of relay X is closed as follows: ground, cont-acts of relay D contacts of relay D 21, and winding of relay to battery and ground. The operation of this relay, however, performs no useful function at this time.

In case theA operator wishes to extend a call to one of the upper groups of trunks. she testsfor an idle trunk in the grow t the signal lamp X is lighted, and places the calling plug into the first idle trunk jack I encountered, which we will assume to be jack 200. The insertion of the plug closes the circuit of the trunk conductors 30 and 31 through the central oflice battery associated with the A operators cord circuit, thereby causing the operation of relay F, which has its windings in series with the windings 100 of the repeating coil. The operation of relay F completes the circuit of relay G as follows: ground, contacts of relay F, 38, winding of relay G, resistance 101, battery to ground. The operation of relay completes the circuit of slow-tooperate relay 1, as follows: ground, lowermost normal contacts of relay H, 40, contacts of relay G, 41,- winding of relay I, 50, nor mal contacts of relays J and J battery to ground.

Relays J,'J a series relation so that the battery connec tion just traced is reached through the higher nnn'ibere-cl trunks. The relayl of the lowest numbered trunk will not beoperat-ed if one of the series relays in a higher numbered trunk is operated. Relay G also lights lamp Fl in the following circuit: ground,

upper contacts of relay G. 42, contacts of relay l i. &3, lower winding of relay H, lamp S. to'battcry and ground. Relay H does not operate in this circuit.

The operation of relay I completes the circuit of slow-to-release relay J. The operation of relay J completes the circuit of slow-to-operate relay K as follows: battery, winding of relay K, contacts of relay J, 16, winding of relay C to ground.

The operation of relay J connectsthe tone source 300 to conductor 36, notifying the A operator th the ephone set f the ll ope a? r is be ng c ected to the trunk.

The operation of relay C completes the circuit of relay D which operates and breaks the circuit of relay E causing the eXt-inguishingof the lamp X thereby indicating to other A operators that the'B operator is b sy.

The operation of relay K disconnects the tone source 300 from the trunk and connects. the B operators telephone set thereto. The operation of relay K also transfers lamp S from ground at relay G to ground through interrupter- 400. Mie flashing of the lamp in step with the interrupter notilies the I? operator that her telephone set is connected to that particular trunk. When the tone is disconnected from the trunk the A operator knows that the B operator is ready to receive the orocr and thereupon gi es "henuishc of the wanted line.

The B operator will thereupon take up the plug 102 of the trunk associated with lamp S and test the called line in the usual manner, and if it is idle will insert the plug. The insertion of the plug in the jack will llfi cause the operation of relay H, theoperation of which will remove. ground from conductor 40, causing the release of relays I,'J and K. The release of relay K disconnects the B operators telephone set from the trunk. As relay C was in series'with relay K it likewise restores and releases relay D again allowing relay E to become operated which lights the lamp X indicating that this particular B pperators position is still occupied and again idle.

The operation of relay H connects ground to the winding of relay G over conductor 39, thereby shunting it and causingit to release. The release of relay'G will open the circuit of lamp S and extinguish it.

The B operator rings in the usual manner. The called subscriber 1 upon removing his receiver operates the trip relay 0, thus releasing relay M to disconnect ringing current from the called line and cause the talking conductors to be closed. 'lVhen the called party answers supervisory relay P is also energized, thereby shunting the upper winding of relay F, thus decreasing the resistance, bridged across conductors 30 and 31 extending to'the A operators position. The decreased resistance allows the'marginal supervisory relay in the A operators cord circuit (not shown) to become energized thereby extinguishing the supervisory lamp which serves-as a notice to the A operator that the called subscriber has answered.

hen the called subscriber replaces his receiver relay P becomes deenergized removing the shunt from the upper winding of relay F, thus restoring the original resistance across the conductors 30 and 31. The

increased resistance allows the supervisory relay in the A operators cord circuit to restore and operate the lamp notifying the operator that the conversation has terminated.

The A operator withdrawing the plug from the trunk jack 200' causes the restoration of relay F which removes ground from conductor 38 extending to relay G allowing it to again operate, this time from ground, at the lower alternate contacts of relay 4. The B operators telephone will not be reconnected as ground has been removed from conductor 40 bythe operation of relay H:

The re-operation of relay G again connects ground to lamp S through lower winding of relay H and contacts of relay K. The lighting of the lamp notifies the B operator that the connection should be taken down and she thereupon removes the plug 102 from the jack of the called line.

In case more than one call is waiting at the time the B operator disposes of a call then the call on the next higher numbered trunk will receive preference. Relays J, J

interval will allow trunk L in the series to become connected to the B operators telephone set in preference to L as relay:

I cannot operate, due toits operating circuit being open at the left-hand back contacts of relay J If two or more calls arrive simulta neously when the B operator is idlethen the preference will be given to a lower numbered trunk as the ground supply for contacts of relays I, I and I is supplied through contacts of relay I of the lower numbered trunk.

In case all of the B operators positions are busy then relays corresponding to relays C and D of each B operators 'posit-ion, such as C D etc., would be energized and likewise relay X. This latter relay is only energized when all the relays corresponding'to relay D are operated as its operating circuit is in series with make cont-acts of allot these relays. In case all relays corresponding to C and D are operated, then ground would be connected over make contacts of relay X to relays cor responding to E and E thereby causing the lighting of all the signal lamps grouped at the A operators positions corresponding to occupied B posit-ions. For illustration, the circuit ofrelay E 'would be completed as follows: ground, contacts of "relay B 17, contacts of relay X, 19, 18,

winding of relay E The operation of re lay E causes lamp X to light. The circuits of all the other lamps would be lighted over similar paths. It will be obvious that the relays corresponding to B at positions not occupied would be in normal position and, therefore, the corresponding lamp at the A position would not be lighted as ground to operate the E relay is sup plied through the contacts of the B relay.

Relay X wouldbe provided with a pair of contacts for each of said lamps and the connection from its winding would pass in series throughvthe contacts of corresponding relays B of each B operators posi tion. y

In case there are a large number of B operators positions, it might be advisable to provide extra relays X having their windings in multiple, and the contacts for causing the lighting of the lamps atthe A operators posit-ions can be arranged in groups, a certain group being allotted to each relay.

WVhile Fig. 1 shows but a single lamp at but one A operators position for each group of trunks, it of course, follows that there would be a lamp for each group of trunks at each A operators position to which trunksare multipled, in which event there would be multiple jacks at each position as shown in Fig. 1.

hat we claim is:

1. In a telephone system, an A oper ators position, a B operators position including a telephone set, means for rendering said telephone set operative when said position is occupied and for rendering said set inoperative when said position is unoccupied, a plurality of trunks extending between said positions, means for automatically connecting said telephone set to said trunks, a signal at said A" operators position associated with said trunks, means responsive to said first means .ior controlling said signal and means responsive to said second means tor ,turther controlling said signal.

2. In a telephone system, an A operators position, a plurality of B operators positions each including a telephone set, a group of trunks extending from each of said B operators positions to said Hi. operatofis position, means at each of said 3 operators positions for automatically connecting the said telephone set to said trunks, a signal at said A operators position common to each said group of trunks, means responsive to said first means for controlling said signals and additional means responsive to the simultaneous operation of all of said first means for further controlling said signals.

3. In a telephone exchange system, the combination of an A and a B operatofis; position, a plurality of trunks therebetween, link circuits at said A position for extending calls over said trunks to said B posi tion, an operators telephone at said B position, means at said B position for automatically connecting said telephone to one of said trunks when it is seized by one of said link circuits and other means at said B position operative it a plurality of said trunks are concurrently seized for automatically controlling the connection of said operators telephone to said seized trunks in a predetermined sequential order.

4. In a telephone exchange system, the combination of an A operators position, a plurality of trunks terminating iii-jacks atsaid position, a signal lamp'common to said jacks, a B operators position including any opcrators telephone common to said plurality oi trunks, means under control of the A operator for selecting an idle one ot said trunk jacks, and automatic means for causing the B operators telephone to be connected to the selected trunk and for controlling the operation of said signal lamp.

5. In a telephone exchange system, an operators position, an operators telephone as sociated therewith, a plurality of trunk circuits incoming to said position, means at said position for controlling the automatic connection of said operators' telephone to said erators position, an operators telephone associated therewith, a plurality of trunk circuits incoming to said position, means at said position for controlling the automatic connection of said operators telephone to said trunks in a predetermined sequential order when a plurality of calls are concur-- rently extended to said position. over said trunk circuits and a signal lamp at said poon individual to each trunk circuit, means tor lighting one of said lamps when a call is extended over its associated trunk circuit and means for flashing said lamp when said operators telephone is connected to the trunk.

7. In a telephone system, a group of trunks, an operators position at the incoming ends of said trunks, means responsive to the occupation of said operators position for rendering said trun rs available for use I and a signal common to said trunks at the outgoing ends thereof responsive to said means. i

S. In a telephone system, a group of trunks, an operators position at the incoming ends of said trunks, an operators headset for connection to said position, means ;responsive to the connection of said headsetto said positlon for rendering said trunks available for use, and a signal common to said trunks at the outgoing ends thereof responsive to said means.

9. In a telephone system, a group oftrunks, an operators position at the incommg ends of said trunks, an operators headset for connection to said position, a relay responsive to the connection of said headset to said position, means responsive to the operation of said relay for rendering said trunks available for use and a signal common to said trunks at the outgoing ends thereof responsive to said relay.

10. In a telephone system, a group of trunks, an operators position at the incoming ends of said trunks, an operators headset for connection to said position, a relay responsive to the connection of said headset to said position, means responsive to the seizure of one of said trunks at the outgoing end thereoi for connecting a source 0]": tone to said seized trunk, means responsive to the operation of said relay for rendering said connection of said source of tone of only momentary duration, and a signal common to said trunks at the outgoing ends thereof' responsive to said relay.

11. In a telephone system, a group of trunks, means at the incoming ends of said trunks for rendering said group of trunks available for use, a signal common to said trunks at the outgoing ends thereof responsive to said means, and additional means responsive to the seizure of any one of said trunks for further controlling said-signal.

12. In a telephone system, a group of trunks an operators position at the incom ing ends of said trunks, means responsive to the occupation of said operators position for rendering said trunks available for use, a signal common to said trunks at the outgoing ends thereof responsive to said means,

and additional means responsive to the seiz-- me of any one of said trunks for further controlling said signal.

13; In a telephone system, a group of trunks, an operators position at the incoming ends of said trunks, means responsive to the occupation of said operators position for rendering said trunks available for use, a signal lamp common to. said trunks at the outgoing ends thereof, means for energizing said lamp responsive to said first means and additional means responsive to the seizure of any one of said trunks for deenergizing said lamp.

In testimony whereof, we have signed our names to this specificationthislfith day of September, 1924.

RAND s; BAILEY. EDGAR P. BROE. 

